1. Field of the Invention
This invention relates to a method for the production of an aqueous dispersion of a long-chain alkyl graft polymer and particularly to the method of the type using a long-chain alkyl graft polymer which is formed by the reaction of a polyamine with an alkyl isocyanate. It further relates to an aqueous release agent formed of the aqueous dispersion.
1.Description of the Prior Art
As long-chain alkyl graft polymers, a polyvinyl alcohol-octadecyl isocyanate adduct [U.S. Pat. No. 2,532,011(1950)] and a polyethylene imine-octadecyl isocyanate adduct [JP-B-40-17,661(1965)] for example, which are produced by a method using an organic solvent as a reaction medium have been heretofore known.
These polymers are invariably used as dissolved in an organic solvent. Practically none of the heretofore known long-chain alkyl graft polymers can be used as diluted with water. The solvent type polymers mentioned above have a disadvantage that the organic solvent deteriorates the work environment, recovery of the used solvent is indispensable to the preclusion of the problem of environmental pollution, the price of the organic solvent itself has been rising in recent years, and the technological innovation has been encouraging switch of the conventional adhesive agents to those of the aqueous and hot melt type. In the circumstances, the desirability of developing an aqueous dispersion of a long-chain alkyl graft polymer has been finding growing recognition.
The solvent type release agents formed of the aforementioned long-chain alkyl graft polymers have been also known. Though these release agents possess excellent properties from the standpoint of quality, they require to use a large amount of an organic solvent during the work of application to a surface and, therefore, entail a step of recovering the solvent to prevent the work environment from deterioration and preclude environmental pollution. Further, the rise of the cost of organic solvent in recent years and the accelerated switch of the conventional adhesive agents to those of aqueous type and hot melt type due to the technological innovation have been urging the development of aqueous release agents.
As an aqueous release agent, a mixture of the emulsion of a copolymer of an acidic group-containing monomer and another monomer with the emulsion of octadecyl ethylene urea [JP-B-52-6,385(1977)], for example, has been known to the art. In the case of the emulsion mixture type aqueous release agent, during the step of drying subsequent to the step of application to a surface, the applied layer of the release agent must be treated at an elevated temperature to induce the reaction between the copolymer and the octadecyl ethylene urea. Thus, this release agent has a disadvantage that it is usable only on a substrate capable of withstanding the elevated temperature.
The aqueous release agents reported heretofore to the art are products obtained by severally emulsifying a long-chain alkyl possessing a functional group such as ethylene urea group, N-methylol group, or a metal salt of carboxylic acid and a polymer film-forming possessing a functional group capable of reacting with the long-chain alkyl and thereafter mixing the resultant emulsions [JP-A-52-6,385(1977) and JP-A-52-7,883 (1977)]. These aqueous release agents must repress their reactivity to be retained stably in the form of emulsion and, nevertheless, complete the reaction of their components during a short span of time spent in the step of drying subsequent to the step of application to a surface. To fulfil these contradictory requirements, the reaction must be performed at an elevated temperature.
An object of this invention, therefore, is to provide a novel method for the production of an aqueous dispersion of a long-chain alkyl graft polymer.
Another object of this invention is to provide a novel aqueous release agent.
A further object of this invention is to provide an aqueous release agent which has no use for a heat treatment at an elevated temperature.